Schmidt SS 20.260 User manual

SCHMIDT®Flow Sensor
SS 20.260
Instructions for Use

Instructions for Use SS 20.260 Page 2
SCHMIDT®Flow Sensor
SS 20.260
Table of Contents
1Important information.......................................................................3
2Application range.............................................................................4
3Mounting instructions.......................................................................4
4Electrical connection......................................................................11
5Signalization..................................................................................12
6Startup...........................................................................................14
7Information concerning operation..................................................15
8Service information........................................................................16
9Technical data ...............................................................................17
10 EC Declaration of conformity.........................................................18
Imprint:
Copyright 2011 SCHMIDT Technology GmbH
All rights reserved
Version 508981.02E
Subject to modifications

Instructions for Use SS 20.260 Page 3
1 Important information
The instructions for use contain all required information for a fast com-
missioning and a safe operation of the SCHMIDT®flow sensor
SS 20.260:
These instructions for use must be read completely and observed
carefully, before putting the unit into operation.
Any claims under the manufacturer's liability for damage resulting
from non-observance or non-compliance with these instructions will
become void.
Tampering with the device in any way whatsoever - with the excep-
tion of the designated use and the operations described in these in-
structions for use - will forfeit any warranty and exclude any liability.
The unit is designed exclusively for the use described below (see
chapter 2). In particular, it is not designed for direct or indirect per-
sonal protection.
SCHMIDT Technology cannot give any warranty as to its suitability
for certain purpose and cannot be held liable for accidental or se-
quential damage in connection with the delivery, performance or use
of this unit.
Symbols used in this manual
The symbols used in this manual are explained in the following section.
Danger warnings and safety instructions –read them care-
fully!
Non-observance of these instructions may lead to injury of per-
sonnel or malfunction of the device.
General note
All dimensions are indicated in mm.
!

Instructions for Use SS 20.260 Page 4
2 Application range
The SCHMIDT®flow sensor SS 20.260 is designed for stationary
measurement of the flow velocity as well as the temperature of air and
gases under atmospheric pressure.
The sensor is based on the measuring principle of the thermal anemom-
eter and measures the mass flow of the measuring medium as flow ve-
locity which is output in a linear way as standard velocity
1
wN (unit: m/s),
based on standard conditions of 1013.25 hPa and 20 °C. Thus, the re-
sulting output signal is independent from the pressure and temperature
of the medium to be measured.
The SCHMIDT® flow sensor SS 20.260 is designed for the use inside
closed rooms and is not suitable for outdoor use.
3 Mounting instructions
General information on handling
The SS 20.260 is a precision instrument with high measuring sensitivity.
In spite of the robust construction of the sensor tip soiling of the inner
sensor elements can lead to distortion of measurement results (see also
chapter 8 Service information). During procedures that could stimulate
soiling like transport, mounting or dismounting of the sensor it is recom-
mended to place the enclosed SCHMIDT Technology protective cap on
the sensor tip and remove it only during operation.
During processes with enhanced risks of soiling such as
transport or mounting the protective cap should be placed onto
the sensor tip.
General installation conditions
The sensor measures the flow speed correctly only in the direction given
on the housing and sensor head (arrow). Make sure that the sensor is
adjusted in flow direction; a tilting of up to ±3° is allowed
2
.
The sensor measures unidirectional and must be adjusted cor-
rectly relative to the flow direction.
A sensor mounted in opposite direction of the flow direction leads to
wrong measuring values (too high).
1
Equates to the real flow velocity under standard conditions
2
Measurement deviation < 1 %
!
!

Instructions for Use SS 20.260 Page 5
The lower measuring range limit is according to the system
requirements 0.2 m/s.
At lower flow velocities (< 2 m/s) the measured medium tem-
perature is too high.
The center of the chamber head is the actual measuring point of the flow
measurement and must be placed in the flow as advantageous as possi-
ble, for example in the middle of a pipe (see Figure 1). Therefore this
point is also used for specification of probe length L (see Figure 2).
Figure 1 Positioning in a pipe
In closed systems the sensor head must be located in the cen-
ter of the pipe.
Installation with low disturbance
Local turbulences of the medium can cause distortion of measurement
results. Therefore, appropriate mounting conditions must be guaranteed
to ensure that the gas flow is supplied to the sensor in a quiet and low in
turbulence state in order to maintain the accuracy specified (see chapter
9 Technical data).
Correct measurements require quiet flow, as low-turbulence as
possible.
An undisturbed flow profile can be achieved if a sufficiently long distance
in front of (run-in distance) and behind (run-out distance) the sensor in-
stallation site (see Figure 2) is held absolutely straight and without dis-
turbances (such as edges, seams, bends etc.). It is also necessary to
pay attention to the design of the run-out distance because disturbances
also generate turbulences against the flow direction.
!
!
!
!
Flow
Direction of measurement

Instructions for Use SS 20.260 Page 6
L
= Length of entire measuring distance
L1
= Length of run-in distance
L2
= Length of run-out distance
D
= Inner diameter of measuring distance
Figure 2
The following Table 1 shows the required straight conduit lengths de-
pending on the pipe inner diameter “D” and the different disturbance
causes.
Flow obstacle upstream of the measuring dis-
tance
Minimum
length of L1
Minimum
length of L2
Light bend (< 90°)
10 x D
5 x D
Reduction / expansion / 90° bend or T-junction
15 x D
5 x D
Two 90° bends in one plane (2-dimensional)
20 x D
5 x D
Two 90° bends (3-dimensional change in direction)
35 x D
5 x D
Shut-off valve
45 x D
5 x D
Table 1
This table lists the minimum values required in each case. If the listed
straight conduit lengths cannot be achieved, measurement accuracy
may be impaired
3
.
Calculation of volume flow
If the cross section area of the pipe is known, the output signal of the
flow speed can be used to calculate the standard volumetric flow of the
medium. By means of a correction factor PF
4
, which depends on the
pipe diameter the measured value can be converted to an averaged flow
wNwhich is constant over the whole pipe cross-section.
Thus, it is possible to calculate the standard volumetric flow of the medi-
um using the measured standard flow velocity in a pipe with known inner
diameter:
3
Alternatively flow rectifier could be used, e.g. honeycomb ceramics
4
Considers parabolic flow profile and sensor obstruction

Instructions for Use SS 20.260 Page 7
EFAwV
wPFw
DA
NN
NN




2
4

Table 2 lists profile factors and volume flow measuring ranges (with cer-
tain sensor measuring ranges) for standard pipe diameters.
Table 2
Inner Min. @
DN [inch]
[mm] PF 0,2 m/s 2,5 m/s 20 m/s 50 m/s
25 25 126.0 0.796 0.30 3.80 30.4 76.1
32 32,8 0.796 0.48 6.05 48.4 121
1 1/4 36,3 0.770 0.57 7.17 57.4 143
40 40 1 1/2 39,3 0.748 0.65 8.17 65.3 163
43,1 0.757 0.80 9.94 79.5 199
45,8 0.763 0.91 11.3 90.5 226
50 50 2 51,2 0.772 1.14 14.3 114 286
57,5 0.777 1.45 18.2 145 363
65 65 2 1/2 70,3 0.786 2.20 27.5 220 549
76,1 0.792 2.59 32.4 259 648
80 80 3 82,5 0.797 3.07 38.3 307 767
100 100 4 100,8 0.804 4.62 57.7 462 1.155
125 125 5 125,0 0.812 7.17 89.7 717 1.794
150 150 6 150,0 0.817 10.4 130 1.040 2.599
180 182,5 0.825 15.5 194 1.554 3.885
200 200 8 206,5 0.829 20.0 250 1.999 4.998
250 10 260,4 0.835 32.0 400 3.202 8.004
300 300 12 309,7 0.840 45.6 570 4.556 11.390
350 14 339,6 0.842 54.9 686 5.491 13.728
400 400 16 389 0.845 72.2 903 7.223 18.058
450 450 18 437 0.847 91.5 1.143 9.147 22.867
500 500 20 486 0.850 114 1.419 11.353 28.383
600 600 24 585 0.854 165 2.066 16.527 41.317
700 700 28 684 0.857 227 2.834 22.673 56.683
800 800 32 783 0.859 298 3.723 29.781 74.452
900 900 36 882 0.862 379 4.740 37.920 94.800
1000 1000 40 980 0.864 469 5.865 46.923 117.308
Nominal
size
Diameter of measuring pipe
Profile
faktor
Measuring range of volumetric flow [m3/h]
Norm value
@ sensor measuring range [m/s]
D
Inner diameter of pipe [m]
A
Cross-section area of pipe [m2]
N
w
Flow velocity in the middle of the pipe [m/s]
N
w
Average flow velocity in the pipe [m/s]
PF
Profile factor (for pipes with circular cross-sections)
EF
Measuring unit factor (conversion to non-SI units)
N
V

Standard volumetric flow [m³/s]

Instructions for Use SS 20.260 Page 8
The measuring unit factor EF serves only for convenient conversion to
non-SI measuring units, for example m3/h (see Table 3).
Measuring unit of diameter D
EF
m
cm
mm
Measuring unit
volumetric flow
m3/s
1
1,0E-04
1,0E-06
m3/min
60
6,0E-03
6,0E-05
m3/h
3600
3,6E-01
3,6E-03
l/s
1000
1,0E-01
1,0E-03
l/min
6,0E+04
6
0,06
l/h
3,6E+06
360
3,6
Table 3
SCHMIDT Technology provides a convenient calculation tool to com-
pute flow velocity or volume flow in pipes for all its sensor types and
measuring ranges. This “Flow Calculator” can be directly used on or
downloaded from SCHMIDT homepage:
http://www.schmidttechnology.de/de/sensorik/download/FlowCalculator.zip
Mounting in a wall
The housing has an external thread M18 x 1 (19 mm long) for direct
mounting on or in the medium separating wall. Its advantage is in the
simplicity of installation without special accessories; however, the im-
mersion depth is defined by the probe length in this case and requires
access from both sides for operation.
Drill a bore in the wall with 13 … 14 mm diameter.
Carefully insert measuring probe with an attached protection sleeve
into the bore so that the mounting block of the enclosure is in contact
with the wall.
Screw on the enclosed fastening nut by hand on the medium side,
turn sensor into required position and tighten fastening nut (SW22)
while holding up the enclosure on the mounting block by means of
SW30.
Angular deviation should not be greater than 3° relative to
ideal position.
Check the set angular position carefully, for example by means of a
spirit level at the hexagonal part of the sensor enclosure.
Finally, remove protective cap from sensor tip.
!

Instructions for Use SS 20.260 Page 9
Mounting with a compression fitting
The sensor is installed using a special compression fitting. Normally, a
sleeve is welded as a connecting piece onto a bore in the medium-
guiding pipe, in which the external thread (G½) of the compression fitting
is screwed (see Figure 3).
Figure 3
L
Probe length [mm]
SL
Length of weld-in sleeve [mm]
AL
Projecting length [mm]
DA
Outer diameter of pipe [mm]
MID
Minimum immersion depth [mm]
E
Setting length of probe [mm]
Bore a mounting opening in a pipe wall.
Weld connecting piece with an internal thread G½ in the center
above the mounting opening on the pipe.
Recommended length of connecting piece: 15 ... 40 mm
If necessary wrap thread using a common sealing tape, for example
made of PTFE.
Screw threaded part of compression fitting one or two turns by hand
into connecting piece then tighten it with a screw wrench (SW27).
Remove compression fitting nut and extract both poetry halves.
Remove protective cap from sensor tip and attach compression fit-
ting nut on sensor probe.
Insert probe in threaded part of the compression fitting, attach poetry
halves and screw on fitting nut manually to such an extent that sen-
sor probe can be inserted without jamming.
L
AL
66SL 32
MET=20
8 E
D
A
MID = 20

Instructions for Use SS 20.260 Page 10
In case of a longer sensor probe push it partly into the pipe as re-
quired.
Always avoid bending of the probe during screwing.
Carefully slide probe so that the center of the chamber head is
placed at the optimum measuring position in the middle of the pipe.
Tighten compression fitting nut slightly by hand so that sensor is
fixed.
Turn sensor manually at its enclosure into required direction and
precise position while maintaining immersion depth.
Angular deviation should not be greater than 3° relative to
ideal position.
Hold sensor and tighten compression fitting nut by turning the fork
wrench (SW17) a quarter of a turn.
Recommended torque: 10 … 15 Nm
Check the set angular position carefully, for example by means of a
spirit level at the hexagonal part of the sensor enclosure.
Mounting accessories
Type / article No.
Drawing
Mounting
Clamp5
a.) 524 916
b.) 524 882
- Internal thread G½
- Material:
a.) Steel, black
b.) Stainless steel 1.4571
Compression fitting
Brass
517 206
51 12
1/2G
SW24
SW27
9
- Immersion sensor
- Pipe (typ.), wall
- Screwing into a welding
stud
- Material:
Brass
PTFE, NBR
Atmospheric pressure use!
Table 4
5
Must be welded
!
!
26,6
34
Rp1/2